So, I got to work on this in my free time, and discovered that I can't make double sided materials via script (not documented anyway).

So unless that gets fixed, you'll have to create and apply your own outline material. I decided not to make the flat-shaded material either, for the sake of consistency. Basically it's just an outliner, not an actual cel-shader-er. Thus, I'm calling it...CelShadurr

Instructions:

Install into your script directory

Click on the turd

Drag anywhere in the workspace. It should create a parametric shape outlining everything

Don't want something outlined? Append the mesh's name with "_noOutline". For example, "mesh01_noOutline". Then double click and OK the CelShadurr shape to regenerate it

You're welcome! Hope it helps, somehow. If you can't tell, I'm not very impressed with what it can('t) do

I forgot to mention it, but you can change the thickness of the outline either by scaling it using the uniform scale tool or by double clicking it and entering it manually. It's measured in Anim8or units.